I’ve posted here in the past when I had an issue that I couldn’t Google my way out of, hoping some kind soul can point me in the right direction once again. Please forgive the long read, but this is going to take some time to explain…I’ll try to condense as much as possible while still giving as much relevant information as I can.

I do IT for a small Architectural firm - they have nine Macs (various mix of laptops and iMac’s, none older than 2012 and all fully updated to 10.12.3) and one Mac Mini used as a file server. Three users are running AutoCAD 2016 natively, four are running Revit 2016 in Windows via Parallels 12 (since AutoDesk does not make a Mac version of Revit). There is also one Windows 8 box running ArchiOffice server. All computers are on a wired connection, hooked into a 24 port Netgear switch via a wall patch panel and are connected to a Wi-Fi network as well.

Several months ago (I can’t give an exact time because the users waited almost two months to report the issue to me, but let’s say in-or-around October) everyone began to experience random freezing. The freeze happens for a matter of seconds - sometimes as little as two seconds, sometimes as much as ten but generally no longer than that. If the user was in MacOS, they’d get the beach ball (the seconds would still tick by on the Finder clock for what that’s worth) but have full mouse control. If they were in Windows via Parallels, they’d have mouse control but otherwise frozen. This happens completely at random - some days it will only happen four or five times in an entire day, some days it will happen a dozen times in an hour. Now here’s the kicker - also completely at random, three or four of the computers will freeze at the exact same time. Never the same computers, never the same number, never the same time - but at random intervals, more than one Mac would freeze simultaneously.

Now here’s the next wrinkle - I have one user that has never experienced a single freeze. She is the only one using the 2016 MacBook Pro.

Ok, so troubleshooting steps….when it became clear more than one Mac would freeze at a time, I just assumed the issue was coming from either the server or the network itself since everyone had those two things in common. I had one user work from an AutoCAD file on their desktop and disconnect from the server, but she still experienced the freezing. I felt like I could rule out the server at that point and turned my attention to the network.

A list of things I’ve tried, in no particular order…I’ve turned off the Wi-Fi just so they’d all be using ethernet, I’ve turned off the ethernet switch and had them use Wi-Fi only. I’ve replaced the switch, replaced the ISP’s router, replaced the Wi-Fi router, replaced every Cat 5 cable in the building. Nothing helped and the freezing continues. The only hardware I haven’t replaced is the actual Cat 5 cable coming from the ISP outside the building since I can’t get to it.

I spent a morning running Wireshark to see if that could tell me anything - it did seem to pick up on TCP retransmission errors when the freezing would occur, but it also picked up those same errors when there was no freezing so I’m not sure if that has anything to do with it or not. I could live with the explanation that something on the network is freaking out the Macs randomly and that I need to find a Network guru or work with the ISP to figure out the problem…if it weren’t for the 2016 MacBook Pro that has never had a single freeze.

In thinking about what’s different about this machine software-wise, all I can really point to is that it came with Sierra out of the box, whereas all the other Macs are older and have been moved from Mavericks or Yosemite to El Cap to Sierra. I’m assuming whatever iOS install that is running the Touch Bar isn’t somehow protecting it from outside network issues. The timing of this also does seem to indicate that it began around the same time that I started moving users to Sierra.

So that’s the very-long and short of it. I’ve Googled this ad nauseam, but can’t find anything quite like it. My next step was to wipe out one of the affected Macs and do a clean install of Sierra, but before I go for the nuclear option that my gut tells me won’t change anything I thought I’d see if anyone kind enough to have gotten through this rambling diatribe might have any thoughts or suggestions. Thank you in advance!

  • Could you give the output of sudo fgrep "kernel[0]" /var/log/system.log for the time of the freeze to troubleshoot? (Or the relevant part of the system.log) Commented Feb 27, 2017 at 16:35

2 Answers 2


perhaps unrelated, but did your client's Macs happen to be upgraded to Sierra around the same time the random freezes began?

my iMac experienced random Finder freezes after upgrading to Sierra. the cause turned out to be Sierra's new iCloud storage feature; your Desktop and Documents folders automatically get moved to the cloud after the Sierra upgrade. that's when the freezing problems started for me. Finder would momentarily freeze every so often (spinning wheel) as it 'synced' the local Desktop & Documents folders with those stored in iCloud. it's a feature i don't need, so i disabled it in iCloud Preferences, and the random Finder freezes stopped.


Was able to capture the system log via the Console app a few seconds after a freeze - as you can see from the numerous iCloud messages, it was immediately clear as to the culprit. All of the Macs in the office that were freezing were logged into the same iCloud account, and as soon as I saw this I looked at the 2016 MacBook Pro that never froze and sure enough - wasn't logged into iCloud at all. Logged out the affected users, and the freezing has stopped. No idea what caused the issue or what exactly its problem was, but for now I'm more than happy to have the workaround. Thanks to user2707001 for putting me on the right track!

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  • Maybe as a comment - Apple starts to have some real software quality issues lately imho, see e.g. my post here apple.stackexchange.com/questions/265428/… .You may try a similar workaround for some unresponsive iCloud server if you want to spend the time. Commented Mar 2, 2017 at 22:36

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